The need for evidence of tampering with packaged products has been a perennial problem and with merchandizing activities more and more centered in large, unsupervised markets the need is greater than ever.
In general, commercially available tamper evident closures for capped containers and bottles have not been satisfactory. They are costly, require additional packaging operations, compromise recycling, may be harmful and give ambiguous results. One or more of these drawbacks are present in currently available seals, bands and multicomponent or multifunctional caps.
One current method for producing such evidence in bottled products calls for the use of wafer-like seals under the cap, sealed to the bottle opening and barring access to the bottle contents until removed. Various methods of application and materials are used for a variety of products. Another method uses a plastic or metal band intimately covering the cap and adjacent neck to prevent access to the cap without removal of the band. Such methods are popularly used on bottles for wine and medicinal products. These wafer-like seals and external bands perform the task of producing evidence of tampering but only if the purchaser or user is familiar with the makeup and appearance of the unopened package because these items are separable from the primary package of cap and bottle and no explicit evidence remains. An additional handicap of such devices is the extra cost in materials, packaging machinery and the cost of operating such machinery.
Another method of providing tamper-evidence to bottles is the use of caps with extended skirt portions which engage restraining features in the bottle neck and which must be torn away in order to remove the cap. This method also suffers from the handicap that no explicit evidence of tampering remains with the primary package, and additional costs are incurred for the extended skirt tearaway feature and the modification to the bottle neck and capping machinery.
Other methods for producing tamper evidence in containers are accomplished using a perforated breakaway lower skirt portion of a metal or plastic cap which is broken away on cap removal and subsequently retained on the bottle neck. This leaves the evidence of tampering on the package where, upon examination, it can be seen as a separated portion of the cap with the implications of tampering. However, plastic caps having this feature may present the problem of indicating tampering falsely when the rings are broken by some other means, such as with soft drinks when simple removal of the bottle from multipackage carriers (which grip the bottle below the cap) break the tamper evidence ring. Metal caps, on the other hand, leave a metal ring on the bottle neck which can have sharp edges and which also present a recycling problem for the bottle. Efforts to solve this problem have resulted in a metal cap with a lower skirt portion which splits radially to leave the cap in one piece when the bottle is opened. Unfortunately, solving the one problem has led to another which is the difficulty in determining whether the bottle has been opened since a careful examination is required, in most instances, to determine whether the skirt has split. Additionally, the effectiveness of the breakaway or split skirt feature in metal caps is a function of the control over the operation of forming the threads and breakaway feature. These are configured "in situ" on the bottle neck by a "roll-on" mechanism. Some incidence of faulty threads and tamper evidence features are known to occur during this operation which may lead to the faulty conclusion that bottles have not been tampered with.
In addition to the current commercial efforts, the patent literature discloses that evidence of bottle tampering may be provided by legends on the closures which express that the container has been opened. (See, for example, U.S. Pat. Nos. 2,201,205 and 2,939,597). These methods, however, are expensive and are based upon closures which require multicomponent assemblies calling for special bottle neck designs.
Other tamper-evident closures are disclosed in U.S. Pat. Nos. 3,935,960, 3,923,198 and 3,896,965. These patents disclose tape closures produced from plastic sheets which adhere to cans and which indicate the cans have been opened by a color change that takes place in the closure where it has been pulled and stressed during removal. The color change mechanism is accomplished in one case through the use of encapsulated coloring agents dispersed in the plastic and in the other case through the use of plastics which exhibit the phenomenon known as stress whitening or opacification as disclosed in U.S. Pat. Nos. 3,433,152, 3,468,774 and 3,887,734. As a tape primary closure these methods are limited by their form and method of application to generally non-resealable containers. As a tape secondary closure they would behave as the "tamper evident" bands discussed above and have the same drawbacks of leaving no explicit evidence of tampering after removal and requiring multicomponent and costly assemblies.
Thus, known tamper-evident closures and packages are beset with drawbacks.